● Covered by 1 source · 1 reportMedium impact1 neutral
Linux Kernel Flaw in ARM64 KVM Allows Guest Read-Write Access to Host Memory
Key points
- CVE-2026-89775 affects ARM64 KVM with nested virtualization.
- Allows guest VMs to read/write host kernel memory.
- Can lead to guest escape and host code execution.
- Fixed in Linux 6.18.51, 7.2.5, and 7.3-rc1.
Vulnerability Details
A newly discovered flaw, tracked as CVE-2026-89775, exists within the Linux kernel's KVM virtualization code specifically for ARM64 processors. This vulnerability allows a guest virtual machine to gain read-write access to a freed piece of host memory. The issue arises when nested virtualization is enabled on the host.
The flaw occurs in the KVM component handling nested virtualization on ARM64. A specific memory arrangement by the guest causes a size calculation to result in zero, leading to the skipping of a crucial TLB invalidation step. This leaves a freed host memory page mapped and writable, allowing the guest to manipulate it 64 bits at a time without hardware intervention.
Impact and Exploitation
Security researcher Hyunwoo Kim, who reported the flaw, states that a guest can exploit this to escape its virtual machine and execute code on the underlying host machine. Additionally, on systems where the /dev/kvm device is accessible to all users, a local user could leverage this bug to achieve root privileges, provided nested virtualization is enabled.
Red Hat Enterprise Linux 10 is listed as affected, while versions 6 through 9 are not. No exploit code has been publicly released, and there is no indication that this flaw has been used in real-world attacks.
Affected Versions and Fixes
The affected code is part of the mainline Linux kernel for ARM64. The vulnerability is present from Linux kernel version 6.17, though the code itself appears in 6.16. The fix has been applied in Linux kernel versions 6.18.51, 7.2.5, and 7.3-rc1. Distributions are expected to incorporate these patches.
Prerequisites for Attack
Exploitation of this flaw requires nested virtualization to be enabled on the ARM64 host. Nested virtualization is an experimental boot-time mode that is off by default and requires Armv8.4 hardware with the FEAT_NV2 feature. Hosts that do not enable nested virtualization are not susceptible to this specific attack path.
✨ This summary was generated by AI from the outlets' reporting listed below. It is not independently verified and may contain errors — check the original sources. How BrevFeed works →
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Primary sources
CVE CVE-2026-897759.3 CRITICALReporting from
A new flaw, CVE-2026-89775, in the Linux kernel's KVM virtualization code for ARM64 processors allows guest virtual machines to read and write host kernel memory when nested virtualization is enabled. This vulnerability can lead to guest escape and arbitrary code execution on the host machine. The issue is fixed in Linux kernel versions 6.18.51, 7.2.5, and 7.3-rc1.